1. Field
The field of the invention is the harvesting of brine shrimp cysts (eggs) from bodies of highly salt concentrated water such as found in the Great Salt Lake of Utah.
2. State of the Art
Brine shrimp eggs are contained within protective spherical cysts which, in the species of concern, float in dense concentrated brine. The cysts exist in huge numbers and have in fact been harvested from shoreline deposits. However, this method of harvest typically results in the inclusion of much debris and foreign material, including sand and the like. This material must subsequently be removed by washing and other procedures at considerable expense before the cysts are in condition for shipment. Shrimp eggs are ultimately caused to hatch and develop into the shrimp, which are then utilized as food for use in shrimp farms and the like producing food for human consumption. More recently, a great deal of interest has developed in harvesting the shrimp cysts distantly from the shore to avoid the contamination from foreign material. The cysts inhabit the top fraction of an inch of the surface of the salt water, They may be harvested as by manual net dipping, utilizing 120 mesh material and the like. Such harvesting methods are practical, but are undesirably labor intensive. Accordingly, other devices have been conceived based upon pumping the cyst rich top layer of water into porous cloth bags or the like, with the brine subsequently draining away and leaving the cysts within the bags. However, the direct pumping of the surface layer appears to be impractical because the available pumping apparatus ingests far too much water along with the cysts, making the bags straining procedure unduly time consuming and inefficient. Accordingly, devices have been conceived and used which attempt to efficiently concentrate the cysts within the brine before pumping into the final receptacle bags. One such device is disclosed in U.S. Pat. No. 4,839,062, being a raft-supported cyst collection device in a funnel configuration. The funnel is submerged in the water so that a portion of its leading upper edge is below the cyst-containing layer of water. The device then depends upon forward motion of the raft to ingest the cyst-containing layer of water, hopefully concentrated sufficiently to be a slurry. The funnel outlet is connected to a hose and pump system to move the slurry from the funnel into the final cyst collection bags. The success or efficiency of the system depends upon maintenance of the funnel level, which is done by a crank and screw device which adjusts the entire funnel in elevation. This adjustment must be constantly changed because of swells, either occurring from wind or from the forward motion of the raft. The maintenance and adjustment of this level is made even more clumsy and ineffective by the use of wedged shape forwardly extending side bars connected directly to the funnel. The converging side bars must be maintained in proper level also and to do so has required the use of a tower, winch and cable assembly mounted on the raft. This adds to the instability of the raft, compounding the tipping and bobbing which of course results in the submergence and raising of the collection funnel erratically. Further difficulty exists because the center of gravity of the raft structure supporting the collection funnel is constantly changing with the transport of water to the bags and the attendant weight, causing the raft to tilt or yaw. Clearly, a need continues to exist for improving the off-shore harvesting of brine shrimp cysts which effectively avoids or minimizes the intake of excess water and the associated foreign material. It is also highly desirable that efficient dewatering be possible in the off-shore operation to simplify the subsequent final processing.